Hikaru Sulu's mother was a consulting agronomist and his father a poet. The family moved around a lot, but had spent some time on the colony world of Ganjitsu. As a 12-year-old, one of the young Sulu's instructors had been George Samuel Kirk, Jr.

Sulu was a lieutenant straight out of Starfleet Academy, graduating in 2264 (making his birth year 2242). He had been on the Academy fencing team but was snubbed by many of his teammates because of his colonist background.

He had looked forward to a first assignment on the Border Patrol, on the Aerfen under Captain Hunter, but Kirk pulled strings to get him on Enterprise as helmsman.

As a commanding officer, Sulu was often dictatorial and, with peers, full of himself. (Chekov's Enterprise, "Walking on Broken Glass")

After Pavel Chekov became captain of the Enterprise-B in the mid-2290s, Sulu alienated Chekov by often condescending to him and by pulling seniority on him during the search for the Jenolen. (Chekov's Enterprise)

At some point in the late 2290s or early 2300s, Sulu's daughter Demora had a daughter, whom she named Alana after a request from her father. On the first meeting between the elder Sulu and his granddaughter, he explained to Demora that she had a half-sister in another timeline. ("World Enough and Time")